A fire, sulfur & bitumen. Ancient romans killed people with toxic tar sands centuries ago.
So what happens when a pipeline of Canadian bitumen (tarsands) meets up with any of the wildfires the usa is plagued with?
Fumes of hell
Chemical warfare was well established by the time the Persians besieged Dura, said Adrienne Mayor, a historian at Stanford University and author of "Greek Fire, Poison Arrow
s & Scorpion Bombs: Biological and Chemical Warfare in the Ancient World" (Overlook Press, 2003).
"There was a lot of chemical warfare [in the ancient world]," Mayor, who was not involved in the study, told LiveScience. "Few people are aware of how much there is documented in the ancient historians about this."
"So the Persians set a trap. Just as the Romans broke through, James said, they lit a fire in their own tunnel. Perhaps they had a bellows to direct the smoke, or perhaps they relied on the natural chimney effect of the shaft between the two tunnels. Either way, they threw sulfur and bitumen on the flames. One of the Persian soldiers was overcome and died, a victim of his own side's weapon. The Romans met with the choking gas, which turned to sulfuric acid in their lungs."
http://www.livescience.com/13113-ancient-chemical-warfare-romans-persians.html
